/*-
 * ========================LICENSE_START=================================
 * Core
 * %%
 * Copyright (C) 2020 Smooks
 * %%
 * Licensed under the terms of the Apache License Version 2.0, or
 * the GNU Lesser General Public License version 3.0 or later.
 *
 * SPDX-License-Identifier: Apache-2.0 OR LGPL-3.0-or-later
 *
 * ======================================================================
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
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 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
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 * =========================LICENSE_END==================================
 */
package org.smooks.engine.resource.config.xpath;

import org.smooks.api.ExecutionContext;
import org.smooks.api.SmooksException;
import org.smooks.api.TypedKey;
import org.smooks.api.resource.config.xpath.SelectorStep;
import org.smooks.api.resource.visitor.sax.ng.BeforeVisitor;
import org.smooks.engine.delivery.fragment.NodeFragment;
import org.smooks.engine.memento.VisitorMemento;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/**
 * Element position counter.
 * <p/>
 * Used for position based XPath predicates.
 *
 * @author <a href="mailto:tom.fennelly@jboss.com">tom.fennelly@jboss.com</a>
 */
public class ElementPositionCounter implements BeforeVisitor {

    private final SelectorStep selectorStep;
    private final TypedKey<String> positionMementoTypedKey = TypedKey.of();

    public ElementPositionCounter(SelectorStep selectorStep) {
        this.selectorStep = selectorStep;
    }

    public SelectorStep getSelectorStep() {
        return selectorStep;
    }

    @Override
    public void visitBefore(Element element, ExecutionContext executionContext) throws SmooksException {
        Integer position = getElementPosition(element, executionContext);
        if (position != null) {
            VisitorMemento<Integer> positionMemento = new VisitorMemento<>(new NodeFragment(element.getParentNode()), this, positionMementoTypedKey, position + 1);
            executionContext.getMementoCaretaker().capture(positionMemento);
        }
    }

    public int getCount(Element element, ExecutionContext executionContext) {
        Integer position = getElementPosition(element, executionContext);
        return position != null ? position : 0;
    }

    protected Integer getElementPosition(Element element, ExecutionContext executionContext) {
        Node parentNode = element.getParentNode();

        if (parentNode != null) {
            VisitorMemento<Integer> positionMemento = new VisitorMemento<>(new NodeFragment(parentNode), this, positionMementoTypedKey, 0);
            executionContext.getMementoCaretaker().restore(positionMemento);

            return positionMemento.getState();
        }

        return null;
    }
}
